Over the past week or so I''ve been researching and trying to implement Collision Detection to my game. I''ve scowered through this forum, looked at the articles and resources section, but haven''t been able to overcome my problem. The game works by a map array MAP[100][100]. It scrolls around this map drawing from these tiles as an example. The problem: ------------ Implementing a collision detection system which checks for collision with different objects(walls, pit lane, other cars) whilst rotating. The collision detection has to be accurate enough to collide around corners. The last game I worked on I used dx7 and ddraw. For the collision detection in that I locked the backbuffer and check certain points depending on where my character was for certain pixel colors. The approach ive tried sofar to solving the problem was creating a "bitmask" for each tile to check against the background. I tried this by having 2 arrays eg: BYTE SCREEN[640][480]; BYTE tile1[64][64]; memcpy(&SCREEN[tilex][tiley],&tile1,sizeof(tile1)); What I was trying to do here was copy the bitmasks to a screen array at a certain point say SCREEN[64][64], for each of my tiles. Filling the screen array. I would then have check points in SCREEN[][] to see if there was a collision. However this didn''t work. Other info is im using DX8.1 and the ID3DXSPRITE interface. Could someone plz give me some alternative approach I could take to solving this problem.

Hey,

I''ve been thinking about a car racing game myself, I haven''t found a solution to how I would like to design my tracks (which would lead to various collision detection methods).

I''ve thought about tile based ideas like yours but I want something more versatile, though I reacon you have the right idea using masks for this type of method. You could have something like a 4 bit mask or something if you wanted to define things like road/grass/impassable/etc.

The only other option I think would be vector type tracks, which I could do in some 3D package, you could place positions of tree, etc as points - this could be easier to convert to 3D....I dunno I''m toying around with the idea still.

The type of game I''m looking to have it like would be circuit breakers from playstation but start with a 3D version.

And your problem....I dont think the memcpy function works in coping arrays chunks like that. memcpy would copy the array into the other large array as a continous chunk of data, but you want each line offset of the small array in the big one. I''m not sure I can explain that much better atm.

Anyway hope you get past that bottleneck, I love them too >:-)

Thanks for your input Smorg. It got me to thinking how about having a bitmask for each tile as I said before.




Then use this structure:

struct tiles{

int x, int y; // position of tile
mask[64][64]; // bitmask

}

then create an array:

tiles tile[number_of_tiles_that_fill_screen]; // 75 fill screen



Every time I draw the tiles onto the screen I could update tile:

tile[number].x = position it plots at;
tile[number].y = position it plots at;
memcpy(&tile[number].mask,&tilebitmask[numberoftile],sizeof(tilebitmask[numberoftile]));

Then when I want to test if there is a collision I use the points from the car.



These points can be rotated to find theyre new x and y value by radius from centre and angle of car.

Then to check if there is a collision:

for (x = 0; x < 75; x ++) // loop thru all the tiles on the screen
{

if (tile[x].x > carposition - 64 && tile[x].x < carposition + 64) // if a tile is near car
{

test = tile[x].mask[car.point.x][car.point.y]; // check for all 4 points on the car

if (test == 1)
{
collision = TRUE;
}

}

}

I haven't fully thought this through and can see a problem with getting the right position in the mask array. Oh and another thing I wont have to update all 75 tiles only 9 as the car will only need to check collision in 9 different angles. But for the time being im doing it as the whole screen.

More thoughts would help

[edited by - Sloth on August 30, 2002 9:13:26 AM]

Hey cult,

I found this webpage that went right into the car physics stuff, but right into means just that....overly complex for a game that I would want to make.

Anyhow, I want to have a car that slides around corners, but it doesn''t work too well with the method I''m trying. Basically I turn the image of the car to a different direction I''m facing. I got this idea from the game trophy at www.clanlib.org.

Let me know if you have a good idea yourself.